1. Field of the Invention
This invention generally relates to drain valves and drain valve systems for use in water supply systems requiring periodic purging of the water supply systems.
2. Description of Prior Art
Generally underground watering systems with drain valves that automatically drain the water from underground water supply pipes to prevent freezing and rupture of the water supply pipes are well known in the art. My U.S. Pat. No. 3,779,276 shows one such drain valve. The drain valve includes a resilient valve member which prevents water from escaping from the underground water system under high water pressures but opens as the water pressure decreases to permit the water in the underground water lines to drain into the surrounding soil.
My U.S. Pat. No. 4,890,640 shows another type of drain valve having a non-extrudable sealing member. This valve is well-suited in locations where pressure surges occur in the water supply line, since the drain valve contains a valve member that is non-extrudable in relation to the discharge opening. Consequently, the drain valve continues to function normally even though high-pressure surges occur which could normally blow out other valve members.
The present invention comprises an improvement over U.S. Pat. No. 3,779,276 by providing a family of drain valves which can be made to operate under different pressures by changing the internal valve member of the drain valve.
One feature of the invention is a drainage system that conserves water by retaining a portion of the water in the underground water lines.
A further feature of the invention is a field modifiable drain valve which can be set to operate under various field conditions.
Still another feature of the invention is a water drainage system having at least two drain valves responsive to different operating pressures to accommodate the different water pressures at different locations in the watering system.